1. Field of the Invention
The present invention relates to an electroacoustic transducer which transduces an electrical signal into a sound.
2. Description of the Related Art
JP-A-8-6558 discloses an electroacoustic transducer which comprises a case in which a pole piece is mounted. The pole piece comprises a base and a core fixed integrally to each other. A coil is placed on the side of the outer periphery of the core. A magnet is placed around the coil with a gap formed therebetween. The coil is placed by directly winding a conductor wire around the core, or by mounting a prewound coil to the core.
However, the following problems arise in the electroacoustic transducer during a step of placing the coil. When the conductor wire is directly wound around the core, there is a possibility that the conductor wire (insulating layer thereof) is damaged by the core which is made of a metal. Also, when a prewound coil is attached to the core, there is a possibility that the core rubs against the conductive wire, damaging the wire, particularly the insulating layer thereof. When the conductor wire (insulating layer thereof) is damaged in this way, the conductor wire may be in contact with a metal portion such as the core to cause a short circuit, thereby lowering the reliability and durability of the electroacoustic transducer.
It may be contemplated to provide an additional part around which a conductor wire is to be wound. In this case, the production cost is increased by the additional part, and a step of attaching the additional part is additionally required.
Moreover, the additional part reduces the capacity of the back space of the electroacoustic transducer. Accordingly, the sound pressure characteristic, particularly that in the bass region is lowered.
The invention has been made in view of these problems. It is an object of the invention to provide an electroacoustic transducer in which, during a step of placing a coil, a conductor wire can be prevented from being damaged without increasing the production cost and the manufacturing steps and reductions in reliability and durability can be suppressed.
According to an aspect of the invention, there is provided an electroacoustic transducer comprising:
a pole piece having a base and a core;
a coil disposed around the core;
a magnet disposed around the coil; and
a case made of a resin material, the case accommodating the pole piece, the coil, and the magnet in an internal space thereof,
wherein a bobbin portion is formed integrally with the case, the bobbin portion elongating toward the internal space of the case; and
the coil is configured by winding a conductor wire around the bobbin portion.
In the electroacoustic transducer of the invention, the bobbin portion is formed integrally with the case which is made of a resin material, and the conductor wire is wound around the bobbin portion to configure the coil. Since the bobbin portion is made of the same resin material as the case, it is possible to prevent the conductor wire (covering layer thereof) from being damaged during a step of winding the conductor wire around the bobbin portion. This configuration prevents a short circuit possibly caused by a damaged conductor wire (coil) being in contact with a metal portion such as the core, and hence it is possible to suppress reductions of the reliability and durability of the electroacoustic transducer.
In the electroacoustic transducer of the invention, since the bobbin portion is formed integrally with the case, another member for winding the conductor wire is not additionally required. Therefore, it is possible to realize simply and at a low cost a configuration in which the bobbin portion can be provided without increasing the production cost and the manufacturing steps, and the conductor wire (covering layer thereof) can be prevented from being damaged.
Preferably, the case comprises an upper case, and a lower case having a coil terminal portion to which an end of the conductor wire is electrically connected, and the bobbin portion is formed integrally with the lower case.
Since the case is configured in this way, the bobbin portion which extends into the internal space of the case can be easily formed.
Preferably, the bobbin portion extends from the lower case to surround the outer periphery of the core, and the base is placed on the lower case, and has a hole through which the bobbin portion is passed.
Since the bobbin portion is formed in this way, it is possible to realize very simply a configuration in which the base can be easily placed on the lower case without interfering with the bobbin portion.
According to another aspect of the present invention, there is provided an electroacoustic transducer comprising:
a pole piece having a base and a core;
a bobbin portion placed to surround an outer periphery of the core;
a coil formed of a conductor wire wound around the bobbin portion; and
a magnet placed around the coil,
wherein the bobbin portion is divided into a plurality of portions along a circumferential direction of the core.
In the electroacoustic transducer of the invention, since the coil is configured by winding the conductor wire around the bobbin portion, it is possible to prevent the conductor wire (covering layer thereof) from being damaged during a step of winding the conductor wire. This configuration prevents a short circuit possibly caused by a damaged conductor wire (coil) being in contact with the core. As a result, it is possible to suppress reductions of the reliability and durability of the electroacoustic transducer.
In the electroacoustic transducer of the invention, since the bobbin portion is divided into plural parts along the circumferential direction of the core, the bobbin portion is intermittently placed as viewed along the circumferential direction of the core, and hence the capacity of the bobbin portion can be reduced. Therefore, a reduction of the capacity of the back space of the electroacoustic transducer can be suppressed as far as possible, so that the sound pressure characteristic can be prevented from being lowered.
Preferably, the transducer further comprises a case comprising: an upper case; and a lower case having a coil terminal portion to which an end of the conductor wire is electrically connected, and the bobbin portion is formed integrally with the lower case.
Since the transducer further comprises a case configured in this way, another part for winding the conductor wire is not additionally required. Therefore, it is possible to realize simply and at a low cost a configuration in which the bobbin portion can be disposed without increasing the production cost and the manufacturing steps, and the conductor wire (covering layer thereof) can be prevented from being damaged.
Preferably, the bobbin portion extends from the lower case to surround the outer periphery of the core, and the core is pressed against the bobbin portion. Since the bobbin portion is formed in this way, the pole piece can be prevented from being detached from the lower case.
Preferably the base is placed on the lower case, and has a hole through which the bobbin portion is passed. Accordingly, it is possible to realize very simply a configuration in which the base can be easily placed on the lower case without interfering with the bobbin portion.